all Python 3Lists (list)function

list.index

search

Return the index of the first matching value; optional start/end narrow the search; raises ValueError if absent.

Syntax

lst.index(value[, start[, stop]])

Unlike str.find there is no "not found" return value: a missing item raises ValueError, so either wrap the call in try or check with in first. The scan is linear and left to right, and with start/end the number you get back is still an index into the whole list, not an offset from start.

Examples

letters = ['a', 'b', 'c', 'b']
print(letters.index('b'))      # → 1
print(letters.index('b', 2))   # → 3

See also

Common errors

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